Internal pipe gripping tools typically have gripping elements that can be inserted into a pipe and forced into contact with the inner wall of the pipe. Once the gripping elements have engaged the inner wall of the pipe, a pulling force may be applied to the gripping tool to pull the gripping tool and pipe. After the pulling operation, the gripping elements may be released from the inner wall of the pipe to allow the gripping tool to be pulled out of the pipe.
U.S. Pat. No. 2,571,619 (“Rusk”) discloses a pipe puller that has a pair of wedge-shaped jaws connected by upper and lower toggle links. The jaws are mounted on an expander wedge. After inserting the pipe puller into a pipe, an auxiliary cable coupled to the upper toggle links is operated such that the jaws ride down the expanded wedge and are forced into frictional contact with the inner wall of the pipe. The toggle links snap into the locked position and keep the jaws in frictional contact with the inner wall of the pipe. With the tool frictionally engaged, another cable coupled to the head of the pipe puller can be used to pull the pipe puller and pipe.
The upper and lower toggle must be moved into the unlocked position in order to be able to release the jaws from frictional contact with the inner wall of the pipe. However, the auxiliary cable is coupled to only the upper toggle link. It does not appear that the auxiliary cable would be effective in moving the lower toggle link to the unlocked position.